1. Field of the Invention
The present invention relates to a planetary ball mill for grinding a matter to be ground, by bringing a mill pot containing grinding medium balls and the matter to be ground into rotation concurrently with revolution.
2. Description of the Related Art
There has been known a planetary ball mill such that revolutional centrifugal forces and rotational centrifugal forces generated in a mill pot (grinding vessel) in rotation during its planetary motion inclusive of rotation and revolution are applied to the matter to be ground and grinding medium balls contained in the mill pot, to cause severe collisions between the matter to be ground and the grinding medium balls, and the matter to be ground is grounded by the resulting compression and shearing.
FIG. 6 shows a general structure of a planetary ball mill described in Japanese Patent No. 2904399, for example. The planetary ball mill 200 has a structure in which the driving force of a motor 201 is transmitted through a transmission chain 202 to a main shaft (revolution turning shaft) 203, mill pots 206 are mounted through rotation shafts 207 on the upper and lower sides to the tips of upper and lower revolution turning arms 204 and 205 extending in the radial direction from the main shaft 203 so that the mill pots 206 can be turned, and a sun sprocket 209 fixed non-turnably on the same axis as the axis of the main shaft 203 and planetary sprockets 210 fixed on rotation shafts 207 are connected by transmission chains 211. With the motor 201 rotated, each of the mill pots 206 is put into rotation by the turning of the rotation shaft 207 while revolving around the main shaft 203.
The planetary ball mill is characterized by an extremely excellent grinding speed owing to the synergistic effect of a high revolutional centrifugal acceleration and a high rotational centrifugal acceleration.